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Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
The horizontal fraction bar was introduced by the Arabs.
In most climates, 8 to 10 glasses of water per day is recommended for adults. The best indicator for adequate fluid intake is frequent, clear urination.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
Anesthesia awareness is a potentially disturbing adverse effect wherein patients who have been paralyzed with muscle relaxants may awaken. They may be aware of their surroundings but unable to communicate or move. Neurologic monitoring equipment that helps to more closely check the patient's anesthesia stages is now available to avoid the occurrence of anesthesia awareness.
![Changes in boreal forest composition along a chronosequence in Quebec. Dates refer to the year of th](https://biology-forums.com/gallery/47/medium_33_17_02_12_6_53_46_20131094.jpeg)
![History of the number of observed sunspots during the last 250 years, which shows the ~11-year solar](https://biology-forums.com/gallery/47/medium_12359_16_06_12_7_11_02.png)